1. Field of the Invention
The present invention relates to an image processing apparatus and an image processing method, and more particularly, relates to a technique for correcting an image signal output from a defective pixel of an image sensor.
2. Description of the Related Art
In recent years, image sensors have been increased in number of pixels in electronic still cameras and video cameras, and with the increase in number of pixels, the importance of correcting image signals output from defective pixels in the image sensors increased. In this situation, a variety of techniques for correcting image degradation caused by defective pixels has been conventionally proposed. In many cases of the prior art, for example, as is proposed in Japanese Patent Laid-Open No. 2008-53886, defect correction for images is performed on the basis of defective pixel information (defective pixel positions and types of defect) on a image sensor retained at a factory.
However, the method as described above has a problem in that sufficient defect correction is not able to be applied, because the method fails to correct defects which are not detected under specific default check conditions in a factory and defects which are caused by aging.
Consequently, some techniques for solving this problem have been proposed. For example, Japanese Patent Laid-Open No. 2003-259221 proposes a technique of providing an image capturing apparatus with a defective pixel detection mode for detecting defective pixels of an image sensor to perform defect correction with the use of position data for defective pixels detected in the detection mode and position data for defective pixels stored in a memory.
However, in the prior art as disclosed in Japanese Patent Laid-Open No. 2003-259221, no special process is applied when the defective pixels detected in the detection mode include a defective pixel in the same position as that of a defective pixel stored in the memory. Therefore, when type information is retained in addition to positional information on defective pixels as in the case of Japanese Patent Laid-Open No. 2008-53886, multiple different pieces of type information may not have been able to be appropriately reflected, even if a defective pixel has multiple different types of defects. As a result, sufficient defect correction may not have been able to be applied for image signals output from the corresponding defective pixel with respect to various shooting conditions.